The invention is directed to a unique configuration for providing engagement between a pin and a spring, which finds particular utility as a hold-down assembly for a vehicle brake. In accordance with another feature of the invention, the spring is p-shaped to minimize overstressing of the spring during assembly and disassembly of the brake mechanism and to prevent unintended spring disengagement.
Various hold down devices and assemblies have been proposed to facilitate assembly and disassembly of brake mechanisms. One such assembly is designated by the reference numeral 10 in FIGS. 1A-1C. The assembly comprises a u-shaped spring 1 and a retaining pin 3. The spring 1 has a pair of slots 5 and 7 to allow the pin 3 to pass therethrough. The slot 5 in leg 9 of the spring is elongated and recesses 13 are provided on opposite sides of the longer side of the slot 5. A cap 15 is provided on one end of the pin 3, and a stop 17 is provided on the other end. The stop 17 is elongate and sized to pass through the narrower dimension of the slot 5 when the pin is in a first orientation and to engage the recesses 13 when the pin is rotated to a second orientation 90 degrees from the first orientation. With the pin in the second orientation, the spring 1 and pin are locked together by reason of the spring force urging the upper leg 9 against the stop 17 at one end and against the backing plate 23 at the other. Thus, this spring assembly holds the brake shoe 21 in position against the backing plate. The brake shoe can be removed by disengaging the pin 9 from the spring 1 by compressing the spring and rotating the spring with respect to the pin to align the stop 17 with the slot 5.
The prior art design shown in FIGS. 1A and 1B is not without its disadvantages. Referring to FIG. 1C, the spring 1 can be overstressed at 25 where the arcuate portion 27 joins the leg 9. In this configuration, only the ends of the legs 9 and 12 contact each other. A substantial part of leg 9 is unsupported and vulnerable to permanent set if the pin load is too great. Further, this overstressing can also contribute to spring and brake mechanism failure.
Other commonly-utilized hold down assemblies have a coil spring and a retaining pin. Like the FIG. 1 assembly, these coil spring-containing assemblies require rotation of the spring or pin for disassembly. Further, the coil spring can be difficult to grab and rotate for removal. Constant removals and installations of these types of springs can also contribute to carpal tunnel syndrome in brake technicians.
U.S. Pat. No. 5,540,310 to Ludtke et al. shows another type of spring and pin arrangement for holding down brake components. In Ludtke et al., the spring has a u-shape similar to that shown in FIG. 1A; however, Ludtke et al. employ a slot in one leg of the spring to facilitate installation and removal of the spring. Ludtke et al. also use a well or recess to maintain engagement between the end of the pin and the spring. However, if the pin end rises up out, of the recess, the spring can disengage from the pin and compromise operation of the brake mechanism.
In light of the disadvantages of the prior art assemblies used in present day brake mechanisms, a need has developed to provide improved hold-down assemblies. The present invention solves this need by providing an improved brake hold down assembly that provides a positive locking mechanism and further eliminates overstressing experienced by prior art springs to minimize the possibility of permanent set or yield during spring compression.
Accordingly, an object of the present invention is a brake hold down assembly employing a positive locking feature to avoid disengagement between the hold down spring and retaining pin.
A further object of the present invention is to provide an improved brake hold down assembly.
Another object of the present invention is a hold down assembly that avoids overstressing of the assembly""s spring component during removal or installation.
Other objects and advantages of the present invention will become apparent as a description thereof proceeds.
In satisfaction of the objects, the invention provides a unique engagement between opposing legs of a spring, which are preferably p-shaped. The spring includes open-ended slots for receiving a retaining pin having a head shaped to cooperate uniquely with the shape of the slot. Thus, an elongate pin body has a cap at each end. At one end, the pin includes a shoulder adjacent a cap. The shoulder is wider than the pin body, but narrower than the adjacent cap. One of the opposing legs of the spring includes an opening at an inward termination of a slot that is slightly wider than the shoulder so that the shoulder can be received in the opening after the pin is slid through the slot and into the opening. When the pin has been moved through the slot and the shoulder is engaged in the opening, engagement between the shoulder and the side of the opening prevents movement of the retaining pin out of the slot and consequent disengagement of the pin from the spring.
A still further aspect of the invention is the combination of a p-shaped spring and the retaining pin for use in a brake mechanism. The p-shaped spring preferably has two parallel, opposed legs and an arcuate portion connecting the legs. The spring is generally p-shaped viewed from the side when the opposing legs are pressed together, which reduces overstressing of the spring during compression.